1. Field of the Invention
The present invention relates to a crimp terminal adapted to be crimped onto an end portion of an electric wire to be wired in an automobile or the like, a terminal-equipped electric wire having the crimp terminal, and production methods for them.
2. Description of the Related Art
As means for attachment of a terminal to an end portion of an insulated electric wire, has been widely used a crimp technique as disclosed, for example, in Patent Document 1: JP 2005-50736A. The crimp is performed by crimping an electric-wire crimp section (e.g., conductor barrel) preliminarily formed in the terminal onto an end portion of a conductor of the insulated electric wire.
However, the above crimp technique involves difficulty in setting a degree of deformation of the electric-wire crimp section. For example, in the case where the electric-wire crimp section is a conductor barrel, it is difficult to set a crimp height thereof. Setting the crimp height to a small value, while having an advantage of reduction in a contact resistance between the conductor barrel and the conductor of the electric wire, involves a high reduction rate of a cross-sectional area of the conductor, which causes a trouble of deterioration in mechanical strength, particularly, in tensile strength against shock load, (strength of the crimp terminal to hold the electric wire). On contrast, setting the crimp height to a large value, while allowing the mechanical strength to be maintained at a high level, involves a trouble of an increase in the contact resistance between the conductor barrel and the conductor of the electric wire.
Especially, in recent years, there has been studied an use of aluminum or an aluminum alloy as a material for a conductor forming an electric wire; the use particularly involves a difficult set of the crimp height. Specifically, the aluminum or aluminum alloy has a surface which is likely to be loaned with an oxide film in which increases the contact resistance; setting the crimp height to a small value enough to sufficiently reduce the contact resistance irrespective of the formation of the oxide film, makes it becomes difficult to sufficiently ensure the mechanical strength.
As means for solving the above problem, Patent Document 1: JP 2005-507396A discloses a technique of simultaneously forming a large-crimp height portion and a small-crimp height portion in the conductor barrel. In this technique, the large-crimp height portion is formed in a distal-end region of the conductor to contribute to the maintained mechanical strength, while the small-crimp height portion contributes to the reduced contact resistance. However, it is difficult to sufficiently ensure the strength of the terminal while forming a stepped portion corresponding to a difference between the two crimp heights. In other words, to ensure sufficient strength of the terminal, there is allowed only a significantly limited difference to be given between the different crimp heights.